In cell based mobile communication systems base stations are provided to communicate with the mobile devices. Such base stations usually have a high frequency radio part, called Radio Equipment (RE), coupled to an antenna for exchanging radio signals with the mobile devices, which RE is controlled by a further part called Radio Equipment Controller (REC). The REC may be located in the base-station cabinet, while the RE is usually located near the antennas. An interface between both parts has been standardized, and is called Common Public Radio Interface (CPRI).
The standard “Common Public Radio Interface (CPRI); Interface Specification V5.0 (2011-09-21)”, as provided on http://www.cpri.info, describes an example of the interface, abbreviated as CPRI. The CPRI configuration may have multiple Radio Equipment Controllers (REC) and/or multiple Radio Equipments (RE) connected point to point in a chain network using very high frequencies (up to 9.8 GHz) for streaming interfacing. Data samples are received at the RE and interfaced to the REC via an IQ data link called a lane, in a data format based on the I and Q components of the modulated signal. Besides IQ data link, CPRI supports further types of communication and management (C&M) data: a Vendor Specific (“VSS”) channel, a HDLC (“slow C&M channel”) and an Ethernet link (“fast C&M channel”).
FIG. 1 shows an example of CPRI connectivity. The Figure shows an example of a base station architecture 100 comprising a CPRI interface 101 between a REC 102 and an RE 103. A further CPRI interface 104 may be provided to interconnect multiple RECs in a chain. As such, the CPRI interface is described in the CPRI V5 and chapter 2 describes the CPRI related parts of the basic radio base station system architecture. The Figure is taken from chapter 2 (see CPRI V5, FIGS. 2 and 2A on page 10) and is further described in chapter 2.2 System Architecture of the CPRI standard.
It is noted that, in large base stations, multiple lanes of I,Q data samples may be used between RE and REC, and between REC and subsequent RECs in the chain. Each REC may locally process data samples of some lanes, and pass samples of other lanes to further RECs. However, the number of lanes for an individual REC is limited, and a substantial part of said lanes may be required to connect to the RE. Hence a limit for the number of useable lanes depends on the actual number of lanes that the first REC in said chain has available, which limit may be unduly restrict extending the base station to handle larger numbers of lanes from the RE. Similar problems may apply to a chain of REs. Furthermore, control data is transferred between units via the lanes of the common public radio interface.